KR102084771B1 - Pseudo capacitor anode material and method for preparing the same - Google Patents

Abstract

In the present invention, a negative electrode material for a water capacitor having excellent non-capacitance characteristics and a method of manufacturing the same are provided.

Description

Cathode material for water capacitors and manufacturing method thereof {PSEUDO CAPACITOR ANODE MATERIAL AND METHOD FOR PREPARING THE SAME}

Cross Citation with Related Application (s)

This application claims the benefit of priority based on Korean Patent Application No. 10-2017-0123725 filed on September 25, 2017, and all contents disclosed in the literature of the Korean patent applications are incorporated as part of this specification.

The present invention relates to a negative electrode material for a water capacitor having excellent non-capacitance characteristics and a method of manufacturing the same.

Electrochemical capacitors are devices that store electrical energy by forming an electrical double layer between the surface of the electrode and the electrolyte. Unlike a battery that generates electricity by a chemical reaction, a capacitor is made of electricity by an electric double layer, so that there is no damage to the electrode itself, and thus the life is almost infinite, and the charging and discharging time is not long. Can be stored. Accordingly, the capacitor is an electrical storage body that can be particularly useful in the field where high power is required.

Recently, as the demand for energy storage device having high energy density and high output increases, research on supercapacitors is actively conducted as an energy storage device having higher energy density than conventional general capacitors and output characteristics superior to lithium ion batteries. have. Such supercapacitors can be classified into electric double layer capacitors (EDLC) and pseudo capacitors according to the mechanism of energy storage mechanism.

EDLC is based on electrochemical phenomena on the surface of carbon materials and shows high output characteristics but is only applied in limited applications due to its relatively low energy density.

To overcome this low capacity of carbonaceous-based EDLCs, charges are stored through faradaic reactions occurring on the surface of nanostructures, and larger capacitances are achieved by using a reversible oxidation / reduction reaction at the electrode / electrolyte interface. There is an active research on the water capacitor which can represent.

However, in the case of water capacitors operated in an aqueous electrolyte, the electrode material for the negative electrode is limited, and research on this is very important. Although a vanadium oxide is known as a representative cathode material, it does not realize the performance to satisfy the demand for improvement of low output characteristics due to low capacitance and low electrical conductivity.

In addition, various manufacturing methods, such as hydrothermal synthesis and precipitation reaction, have been studied and proposed to improve the capacitance and output characteristics by controlling the properties of vanadium oxide, but the electrochemical performance has not been greatly improved.

Korean Laid-Open Patent No. 2001-0027907 (2001.04.06 published)

Accordingly, an object of the present invention is to provide a negative electrode material for a water capacitor having excellent non-capacitance characteristics and a method of manufacturing the same.

According to an embodiment of the present invention, a metal oxide; And a composite of a metal oxide-conductive inorganic material comprising a conductive inorganic material combined with the metal oxide, wherein the composite is doped with one or more doping elements selected from the group consisting of transition metals and amphoteric metal elements. It provides a negative electrode material for a water capacitor.

In addition, according to another embodiment of the present invention, after mixing the metal oxide, the conductive inorganic material and the raw material of the doping element, adding and reacting by adding a carboxylic acid complexing agent; And it provides a method of producing a negative electrode material for a water capacitor, comprising the step of heat-treating the resulting reactant.

In addition, according to another embodiment of the present invention, a cathode and a water capacitor for a water capacitor including the negative electrode material are provided, respectively.

In the negative electrode material for water capacitor according to the present invention, a complex of a metal oxide and a conductive inorganic material has a plate-like laminated structure, which facilitates access of the electrolyte to the electrode surface, and is doped by a doping element, whereby the doping element and the conductive inorganic The increased charge transfer between materials can dramatically improve capacitance and output characteristics when applied to the cathode of a water capacitor.

FIG. 1A is a graph showing X-ray diffraction (XRD) results of vanadium oxide used in Example 1, FIG. 1B is a scanning electron microscope (SEM) observation photograph, and FIG. 1C is an enlarged view of the circle display portion in FIG. 1B.
FIG. 2A is a graph showing the results of XRD analysis on the vanadium oxide used in Example 2, FIG. 2B is an SEM photograph, and FIG. 2C is an enlarged view of the circle display portion in FIG. 2B.
3A to 3C are SEM images of the composite of the vanadium oxide-carbonaceous material prepared in Example 1 at various magnifications.
4A to 4C are SEM photographs observed at various magnifications of the composite of the vanadium oxide-carbonaceous material prepared in Example 2. FIG.
FIG. 5 is a SEM photograph of the composite of the vanadium oxide-carbonaceous material prepared in Example 3. FIG.
6 is a SEM photograph of the composite of the vanadium oxide-carbon material prepared in Comparative Example 1. FIG.
In FIG. 7, a) is an electron microscope photograph of the negative electrode material prepared in Example 1, and b) is an elemental analysis result using an energy dispersive spectrometer (EDS).
In FIG. 8, a) is an electron microscope photograph of the negative electrode material prepared in Example 2, and b) is an EDS elemental analysis result.
9 is a CV graph measured by cyclic voltammetry (CV) of the negative electrode material prepared in Example 1. FIG.
FIG. 10 is a CV graph measured by cyclic voltammetry of the negative electrode material prepared in Example 2. FIG.
11 is a CV graph measured by cyclic voltammetry of the negative electrode material prepared in Example 4. FIG.
12 is a CV graph measured by cyclic voltammetry of the negative electrode material prepared in Comparative Example 2. FIG.
FIG. 13 is a CV graph measured by cyclic voltammetry of the negative electrode material prepared in Comparative Example 3. FIG.
14 is a graph evaluating output characteristics of the negative electrode materials of Examples 1 to 3 and Comparative Example 1. FIG.

In the present invention, the terms first, second, etc. are used to describe various components, which terms are used only for the purpose of distinguishing one component from other components.

Also, the terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise", "comprise" or "have" are intended to indicate that there is a feature, number, step, component, or combination thereof, that is, one or more other features, It is to be understood that the present invention does not exclude the possibility of adding or presenting numbers, steps, components, or combinations thereof.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific form disclosed, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Hereinafter, the present invention will be described in more detail.

Cathode material for a water capacitor according to an embodiment of the present invention,

Metal oxides; And a complex of metal oxide-conductive inorganic material including a conductive inorganic material combined with the metal oxide,

The composite is doped with one or more doping elements selected from the group consisting of transition metals and amphoteric metal elements.

Specifically, in the present invention, when preparing a negative electrode material for a metal oxide-based water capacitor, a complex of a metal oxide-conductive inorganic material having a plate-like laminated structure is formed by using a carboxylic acid complexing agent, and the composite is By doping with the doping element, the charge transfer between the doping element and the conductive inorganic material is increased, and the access of the electrolyte to the electrode surface is facilitated, and the capacitance and output characteristics can be drastically improved.

More specifically, when complexing the metal oxide and the conductive inorganic material, reactive functional groups present on the surface of the conductive inorganic material by adding a carboxylic acid complexing agent, for example, hydroxyl-based functional groups present on the surface of the carbon-based material And the metal oxide react to form a bond. At this time, when the metal oxide has a plate-like structure like vanadium oxide, the plate-like stacked structure is formed by laminating a plurality of plate-like vanadium oxides interposed therebetween. As a result, the accessibility of the electrolyte to the surface of the electrode may be excellent, and the capacitance and output characteristics of the water capacitor including the same may be further improved.

In addition, according to one embodiment of the invention, the effect can be further improved through the optimization of the content of the metal oxide and the conductive inorganic material in the composite. Specifically, in the composite, the metal oxide may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the conductive inorganic material. When the content of the metal oxide is within the above-mentioned range, it is possible to obtain excellent capacitance and output characteristics improvement effect without fear of deterioration of the effect due to the aggregation phenomenon and uneven dispersibility of the composite or the reduction of the relative conducting path of the carbon-based material. Can be represented. More specifically, the metal oxide may be included in 10 to 15 parts by weight based on 100 parts by weight of the conductive inorganic material.

On the other hand, the conductive inorganic material in the composite is specifically carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanorods (carbon nanorods; CNRs), steam growth carbon fibers (VGCF), graphene (graphene), Or a carbon-based material such as activated carbon, among others, may be a fibrous carbon-based material such as CNT, CNF, CNRs, or VGCF. One of the above materials may be used alone or in combination of two or more thereof.

In the present invention, 'fibrous' is the ratio of the long axis (length) passing through the center of the carbonaceous material and the short axis (diameter) perpendicular to the long axis and passing through the center of the carbonaceous material, that is, the aspect ratio (= length / diameter ratio). ) Is longer than 1, long in the longitudinal direction, and encompasses rods, tubes, fibers, or similar forms thereof.

In addition, the conductive inorganic material may be Maxine (Mxene) known as the electromagnetic shielding material. The maxine has a layered structure composed of a layer of the front transition metal (M) and an X layer including at least one of carbon and nitrogen, similar to graphene, and exhibits excellent conductivity. The front transition metal (M) may be Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and the like, and may include any one or two or more thereof.

Specifically, in the Maxine _{Ti 2 C, (Ti 0.} 5, Nb 0. 5) 2 C, V 2 C, Nb 2 C, Mo 2 C, Ti 3 C 2, Zr 3 C 2, Hf 3 C 2 Carbide-based materials such as Nb ₄ C ₃ , Ta ₄ C ₃ , Mo ₂ TiC ₂ , Cr ₂ TiC ₂ , or Mo ₂ Ti ₂ C ₃ ; Nitride-based materials such as Cr ₂ N or Ti ₄ N ₃ ; Carbonitride-based materials such as Ti ₃ CN, and the like, and any one or two or more of them may be used. Among these, any one or two or more materials of Ti ₃ C ₂ , Nb ₂ C and V ₂ C may be used, which may be porous and thus provide a wider specific surface area.

Considering the remarkable effect of the control of the conductive inorganic material, the conductive inorganic material may be more specifically CNT. In the case of CNT, the hollow core is included in the center, and the ballistic electron tunneling effect and the excellent strength of the particle shape during charging / discharging can exhibit a better effect in terms of capacitance improvement. More specifically, the diameter may be 1 nm to 200 nm, or 5 nm to 50 nm, or 5 to 20 nm CNT.

In the present invention, the diameter of the CNT can be measured according to a conventional method such as scanning electron microscope observation.

In addition, the carbon nanotubes may be specifically single-walled, double-walled or multi-walled carbon nanotubes, it may be a multi-walled CNT that can exhibit excellent electrical and mechanical properties due to its unique structure.

In the composite, the metal oxide may be an oxide including at least one metal selected from the group consisting of V, Sn, Ru, Ir, Ta, Mn, Mo, and Ti. It may be a metal oxide having, and more specifically, it may be a vanadium oxide such as vanadium pentoxide (V ₂ O ₅ ).

When the vanadium oxide is used is not particularly limited in shape and particle size, the shape change may occur according to the type of carboxylic acid complexing agent, but the vanadium oxide is to improve the capacitance by increasing the contact area with the electrolyte It may have a plate shape.

On the other hand, in the present invention, the "plate shape" is a structure in which two surfaces corresponding or facing each other are flat, and the size in the horizontal direction is larger than the size in the vertical direction. flake), scales, and the like.

In addition, the composite further includes one or more doping elements selected from the group consisting of transition metals and amphoteric metal elements.

Specifically, the doping element may be included doped with a metal oxide, a conductive inorganic material or both in the composite. More specifically, it may be included in a crystal structure of a metal oxide or a conductive inorganic material, or may be located through physical or chemical bonding to the surface of these materials. In particular, when the doping element is doped into the crystal structure of the metal oxide, the stability of the crystal structure can be improved, and when doped with a conductive inorganic material, the charge transfer between the doping element and the carbon-based material increases, thereby increasing the capacitance And the improvement effect of the output characteristic can be further improved.

Specifically, the doping element may be a transition metal element such as Mn, Cr, Cu, Mo, Ni, Ti, or the like; Or an amphoteric metal element such as Al, Zn, Sn, Bi, or the like, and any one or two or more of these may be used. Among them, any one or two or more elements selected from the group consisting of transition metals containing Mn, Cr, and Mo, and an amphoteric metal atom of Al may be improved due to an increase in electrical conductivity due to an increase in charge mobility on the surface of the electrode material. It can exhibit an excellent capacitance improvement effect, more specifically at least one of Mn and Al, even more specifically Mn may be used.

In addition, when the doping element to the doping element through the optimization of the doping content it can further improve the capacitance improvement effect according to the doping. Specifically, the doping element may be included in an amount of 0.1 to 30 atomic%, more specifically 0.1 atomic% or more, or 0.3 atomic% or more, based on the total atomic weight of the member elements constituting the complex. Up to 10 atomic%, or up to 5 atomic%.

More specifically, in the composite, when the metal oxide is vanadium oxide, the conductive inorganic material is carbon nanotube, and the doping element is at least one of Al and Mn, the capacitance and output characteristics of the water capacitor are different. It can be further improved, and the effect can be further improved if the content is optimized in the above combination.

On the other hand, the negative electrode material for the water capacitor, a step of reacting by adding a carboxylic acid complexing agent after mixing the metal oxide, the conductive inorganic material and the raw material of the doping element (step 1); And a step (step 2) of heat treating the resulting reactant. Accordingly, according to another embodiment of the present invention, a method of manufacturing a negative electrode material for a water capacitor is provided.

Specifically, in the method of manufacturing a negative electrode material for a water capacitor, step 1 is a step of mixing and reacting a metal oxide, a conductive inorganic material, a raw material of a doping element, and a carboxylic acid complexing agent.

The metal oxide and the conductive inorganic material are as described above, and may be used in an amount to satisfy the content range of the metal oxide and the conductive inorganic material included in the above-described composite. In the case of a metal oxide, hydrogen peroxide solution; Or in the solution phase dissolved in an acid such as hydrochloric acid, in the case of a carbon-based material can be used in a dispersion state dispersed in water or a dispersion medium such as carboxymethyl cellulose.

As a raw material of the doping element, any one or two or more mixtures selected from the group consisting of sulfate, nitrate, chloride, acetate and carbonate containing a doping element may be used, wherein the doping element is as described above. . More specifically, sulfates containing doping elements, more specifically sulfates containing at least one of Mn and Al may be used.

The amount of the raw material of the doping element may be determined within the content range of the doping element in the composite as described above.

The carboxylic acid-based complexing agent also introduces reactive functional groups such as carboxyl groups, hydroxyl groups, or amino groups to the surface of the conductive inorganic material to provide nucleation sites for the deposition of metal oxides. As a result, the bonding between the conductive inorganic material and the metal oxide is promoted, thereby forming a complex of a metal oxide-conductive inorganic material. When the metal oxide has a plate-like structure, a composite of a plate-like stacked structure is formed. In addition, the carboxylic acid-based complexing agent may form a chelate structure with a metal ion in the electrolyte composition, such chelate structure may increase the charge and discharge capacity of the battery. In addition, the carboxylic acid-based complexing agent can improve the stability and reactivity of metal ions, suppress side reactions, reduce internal resistance, and the like.

The carboxylic acid-based complexing agent is a compound containing at least one carboxyl group in the molecule, specifically formic acid, acetic acid, propionic acid, butyric acid, valeric acid acid), hexanoic acid, heptanoic acid, caprylic acid, nonanoic acid, decanoic acid, undecylenic acid, lauryl acid ( monocarboxylic acids such as lauric acid, tridecylic acid, myristic acid, pentadecanoic acid, or palmitic acid; Oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, Azelaic acid, sebacic acid, maleic acid, fumaric acid, glutaconic acid, glutaconic acid, traumatic acid, muconic acid, phthalic acid ( dicarboxylic acids such as phthalic acid), isophthalic acid or terephthalic acid; Polyhydric carboxylic acids having three or more carboxyl groups, such as citric acid, isocitric acid, aconic acid, or melic acid, and any one of them, or Mixtures of two or more may be used. In addition, as the carboxyl complexing agent, an amino acid further including an amino group together with a carboxyl group may be used. Specific examples include glutamine, lysine, histidine, serine, threonine, tyrosine, cystine, cysteine, arginine, proline, glutamic acid, aspartic acid, asparagine, glutamine, and the like. Can be used.

Among these, acetic acid, citric acid, aspartic acid, or mixtures thereof may be used, and more specifically, L-aspartic acid may be used in view of the effect of a better complexing agent.

The carboxylic acid-based complexing agent may be used in 1 to 50 molar ratio, more specifically 4 to 40 molar ratio with respect to 1 mole of the raw material of the doping element. In addition, the carboxylic acid-based complexing agent is 200 to 1000 parts by weight, more specifically 200 to 500 parts by weight, and even more, based on 100 parts by weight of the metal oxide under conditions satisfying the content ratio range of the doping element to the raw material Specifically, it may be used in 300 to 400 parts by weight. When used in the above content range, it is possible to exhibit a sufficient complexing agent effect without fear of occurrence of side reactions due to the residual of the unreacted complexing agent.

The carboxylic acid-based complexing agent may be a solid or a liquid, and may be added in the form of a solution or a dispersion. More specifically, it may be added in the form of a solution dissolved in a mixture of water and acid. At this time, the acid serves to assemble and maintain the nanoparticles in the form of a plate-like structure, specifically, ascorbic acid or hydrochloric acid may be used, and the amount of 5 to 20mml with respect to 100ml of the water. Can be used.

The reaction of the metal oxide, the conductive inorganic material, the raw material of the doping element and the carboxylic acid complexing agent may be carried out by adding a carboxylic acid complexing agent after mixing the metal oxide, the conductive inorganic material, and the raw material of the doping element. have.

In this case, the metal oxide, the conductive inorganic material, and the mixing of the raw material of the doping element may be mixed according to a conventional method, and may further include a step for homogeneous mixing, such as stirring.

In addition, after mixing the metal oxide, the conductive inorganic material, and the raw material of the doping element, the alcohol compound may be further added before the carboxylic acid complexing agent is added.

The alcohol compound serves to increase the synthetic yield, specifically, ethanol and the like can be used. The alcohol compound may be added in an amount of 100 to 200 parts by weight based on 100 parts by weight of the mixture of the metal oxide, the conductive inorganic material, and the raw material of the doping element.

In addition, the reaction of the metal oxide, the conductive inorganic material, the raw material of the doping element and the carboxylic acid complexing agent may be carried out at 40 to 80 ℃, more specifically at 60 to 70 ℃. When performed in the above temperature range, the reaction can be carried out with excellent efficiency without fear of overreaction or unreacted.

In addition, a process such as reflux may be optionally further performed to increase the reaction efficiency.

As a result of the reaction of the metal oxide, the conductive inorganic material, the raw material of the doping element and the carboxylic acid complexing agent, the reactant is precipitated.

For the precipitated reactant, a separation process according to a conventional method such as centrifugal separation and an impurity removal process using a washing solvent such as water and ethanol may be performed on the separated reactant.

In addition, a drying process for the separately washed reactant may optionally be further performed. The drying process may be performed using a conventional method, but in the present invention, a freeze-drying method may be used because of maintaining the composite shape of the plate-like structure and preventing the aggregation phenomenon during drying.

Next, step 2 is a step of heat-treating the reactants obtained in step 1 to prepare a negative electrode material.

The reactant obtained in step 1 is a state in which a raw material of a doping element is bonded to a complex formed by combining a metal oxide with a conductive inorganic material through a functional group derived from a carboxylic acid compound. The doped element is doped in an elemental state to the composite of the plate-like laminated structure interposed in the conductive inorganic material to obtain a negative electrode material contained.

The heat treatment process may be carried out at 250 to 350 ℃, more specifically may be carried out at 270 to 300 ℃. When performed within the above temperature range, it is possible to obtain a negative electrode material with excellent efficiency without fear of generation of side reactants due to unreacted and overreacted.

The negative electrode material prepared according to the above-described manufacturing method has a plate-like laminated structure of a complex of a metal oxide and a conductive inorganic material, which facilitates access of the electrolyte to the surface of the electrode, and is doped by a doping element, whereby The increase in charge transfer between inorganic materials can dramatically improve the capacitance and output characteristics when applied to the cathode of the water capacitor.

Accordingly, according to another embodiment of the present invention, there is provided a composition for forming a negative electrode for a water capacitor comprising the negative electrode material and a negative electrode for a water capacitor manufactured using the same.

Specifically, the negative electrode composition for water capacitor may include the negative electrode material described above, and may further include at least one of a binder and a conductive material.

The conductive material is used to impart conductivity to the cathode, and may be used without particular limitation as long as the conductive capacitor has electronic conductivity without causing chemical change. Specific examples thereof include graphite such as natural graphite and artificial graphite, or carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, carbon fiber, and the like. One or two or more mixtures may be used. More specifically, carbon black or acetylene black may be used. The conductive material may be included in an amount of 10 to 30 parts by weight based on 100 parts by weight of the negative electrode material.

In addition, the binder serves to improve adhesion between the negative electrode material particles and adhesion of the negative electrode to the negative electrode and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC). ), Starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubbers, or various copolymers thereof, and the like, and one or more of these may be used. Of these, binders of fluorine-based polymers such as PVDF and PTFE may be used, which may exhibit higher stability to the electrolyte. The binder may be included in an amount of 10 to 20 parts by weight based on 100 parts by weight of the negative electrode material.

In addition, the negative electrode in the water capacitor may be manufactured according to a conventional method except for using the composition for forming the negative electrode. In one example, the composition for forming the negative electrode may be prepared by coating on a current collector, such as copper aluminum, nickel or stainless steel, followed by pressing and drying.

According to another embodiment of the present invention, an electrochemical device including the cathode is provided. The electrochemical device may be specifically a capacitor, and more specifically, may be a water capacitor.

The water capacitor specifically includes a positive electrode and a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the negative electrode is as described above.

In addition, since the configuration and manufacturing method of the water capacitor may be performed according to a conventional method, a detailed description thereof will be omitted.

The invention is explained in more detail in the following examples. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited by the following examples.

Example 1

0.9 g of V ₂ O ₅ , 30 ml of deionized water, and 20 ml of H ₂ O ₂ were added to a round flask and stirred. Here, CNT 6g (30% of CNT, CNT is added as a dispersion dispersed in CMC (carboxymethylcellulose) in 30 ml of deionized water, which means CNT content contained in the added dispersion (CNT concentration in dispersion = 5% by weight). And CNT diameter = 9-11 nm) was added, and 0.5 mmol of Al ₂ (SO ₄ ) ₃ was added and mixed as a doping element raw material. After further 100 ml of ethanol was added, 20 ml of L-aspartic acid (corresponding to 400 parts by weight based on 100 parts by weight of 4 moles / V ₂ O ₅ based on 1 mole of doping element) and 70 ml of deionized water were added to the resulting mixture. And a solution prepared by mixing 5 ml of 6N HCl, and refluxed at 60 ° C. for 12 hours. The precipitated material was separated by centrifugation and washed with deionized water and ethanol to remove impurities. The resultant product was lyophilized for 3 days, and then heat-treated in a tube furnace at 270 ° C. for 12 hours to prepare an Al doped anode material for the metal oxide-CNT composite of V ₂ O ₅ .

Example 2

Except for using MnSO ₄ 1mmol instead of Al ₂ (SO ₄ ) ₃ 0.5mmol in Example 1, it was carried out in the same manner as in Example 1, to the metal oxide-CNT complex of V ₂ O ₅ A negative electrode material doped with Mn was prepared.

Example 3

A metal oxide of V ₂ O ₅ was carried out in the same manner as in Example 1, except that 1 mmol of Cu (NO ₃ ) ₂ was used instead of 0.5 mmol of Al ₂ (SO ₄ ) _{3 in} Example 1. Cu-doped negative electrode material was prepared for the -CNT composite.

Example 4

0.9 g of V ₂ O ₅ , 30 ml of deionized water, and 20 ml of H ₂ O ₂ were added to a round flask and stirred. Here, 60 g of graphene oxide in 30 ml of deionized water (60 g of graphene oxide, graphene oxide is added as a dispersion dispersed in this case, which means 60 g of graphene oxide content contained in the dispersed solution (graphene in dispersion) Oxide concentration = 5% by weight), and mixed by adding 1 mmol of MnSO ₄ as a doping element raw material, after adding 100 ml of ethanol, 20 ml of L-aspartic acid, 70 ml of deionized water, and 6N HCl. A solution prepared by mixing 5 ml was dropped and refluxed for 12 hours at 60 ° C. The resultant precipitated material was separated by centrifugation and washed with deionized water and ethanol to remove impurities. After freeze-drying for 3 days, heat treatment was carried out for 12 hours at 270 ℃ temperature in a tube furnace, Mn-doped negative electrode material for the metal oxide-graphene composite of V ₂ O ₅ Was prepared.

Comparative Example 1

Except not using the doping element raw material in Example 1 was carried out in the same manner as in Example 1, to prepare a negative electrode material in the form of a metal oxide-CNT composite of the undoped V ₂ O ₅ .

Comparative Example 2

0.9 g of V ₂ O ₅ , 30 ml of deionized water, and 20 ml of H ₂ O ₂ were added to a round flask and stirred. MnSO ₄ 1 mmol was added thereto and mixed as a doping element raw material. After addition of 100 ml of ethanol, a solution prepared by mixing 20 ml of L-aspartic acid, 70 ml of deionized water and 5 ml of 6N HCl was added dropwise to the resulting mixture, and refluxed at 60 ° C. for 12 hours. The precipitated material was separated by centrifugation and washed with deionized water and ethanol to remove impurities. The resultant product was lyophilized for 3 days, and then heat-treated in a tube furnace at 270 ° C. for 12 hours to prepare a negative electrode material doped with Mn in a metal oxide of V ₂ O ₅ .

Comparative Example 3

1.8 g of MnO ₂ , 30 ml of deionized water, and 20 ml of H ₂ O ₂ were added to a round flask and stirred. Here, CNT 6g (30% of CNT, CNT is added as a dispersion dispersed in CMC (carboxymethylcellulose) in 30 ml of deionized water, which means CNT content contained in the added dispersion (CNT concentration in dispersion = 5% by weight). And CNT diameters = 9-11 nm) were added and mixed. After addition of 100 ml of ethanol, a solution prepared by mixing 20 ml of L-aspartic acid, 70 ml of deionized water and 5 ml of 6N HCl was added dropwise to the resulting mixture, and refluxed at 60 ° C. for 12 hours. The precipitated material was separated by centrifugation and washed with deionized water and ethanol to remove impurities. The resulting product was lyophilized for 3 days and then heat treated for 12 hours at 270 ° C. in a tube furnace to prepare a negative electrode material of undoped MnO ₂ metal oxide-CNT composite.

Experimental Example 1

The vanadium oxides used in Examples 1 and 2 were analyzed by X-ray photoelectron spectroscopy (XRD), and the crystal structure was observed using a scanning electron microscope (SEM). The results are shown in FIGS. 1A to 1C and 2A to 2C, respectively.

FIG. 1A is a graph showing the results of XRD analysis on the vanadium oxide used in Example 1, FIG. 1B is an SEM photograph, and FIG. 1C is an enlarged view of the circle display portion of FIG. 1B.

2A is a graph showing the results of XRD analysis on the vanadium oxide used in Example 2, FIG. 2B is an SEM photograph, and FIG. 2C is an enlarged view of the circle display portion of FIG. 2B.

As shown in FIGS. 1A to 1C and 2A to 2C, it can be seen that the vanadium oxide used in Examples 1 and 2 has a plate-like structure.

In addition, each negative electrode material prepared in Examples 1 to 3 and Comparative Example 1 was observed by SEM. The results are shown in FIGS. 3A to 6, respectively.

3A to 3C are SEM images of the composite of the vanadium oxide-carbon material prepared in Example 1 at various magnifications, and FIGS. 4A to 4C are the composite of the vanadium oxide-carbon material prepared in Example 2 SEM photographs observed at various magnifications. 5 and 6 are SEM photographs of the composite of the vanadium oxide-carbonaceous material prepared in Example 3 and Comparative Example 1, respectively.

As a result, it can be seen that the composites of the vanadium oxide-carbonaceous materials of Examples 1 to 3 and Comparative Example 1 have a structure in which a carbonaceous material is interposed between plate-shaped vanadium oxides.

In addition, each of the negative electrode materials prepared in Examples 1 and 2 was observed with an electron microscope, and elemental analysis was performed using EDS. The results are shown in FIGS. 7 and 8, respectively.

As a result of the analysis, it can be seen that the negative electrode materials of Examples 1 and 2 are doped with Al or Mn doping element in the composite of the vanadium oxide-carbon-based material having a plate-like laminated structure (Al doping amount in Example 1 (composite) Based on total component atomic content): 0.3 atomic%, Mn doping amount in Example 2 (based on total composite atomic content: 1.08 atomic%).

Experimental Example 2

The CV graphs were measured by cyclic voltammetry (CV) for each of the negative electrode forming compositions prepared in Examples 1, 2 and 4, and Comparative Examples 2 and 3.

In detail, PVDF was mixed in a weight ratio of 7: 2: 1 as the negative electrode material, the carbon black, and the binder prepared in Examples 1, 2 and 4, and Comparative Examples 2 and 3 to prepare a composition for forming a negative electrode. The glass was coated on a glass carbon electrode (GCE), dried in vacuo, and dried at 70 ° C. for 24 hours. 1 M Li ₂ SO ₄ electrolyte was impregnated into the prepared electrode, stabilized, and a cyclic scanning potential test was performed using a platinum counter electrode and an SCE reference electrode. It measured in the voltage range of -1.1--0.2V at the potential scan speed of 10 mW / s.

The capacitance per unit mass depends largely on the content of vanadium oxide and the specific surface area of the negative electrode material, and can be calculated by dividing the current value appearing at the cyclic scanning potential by the scanning speed and the mass of the electrode active material. The results are shown in FIGS. 9 to 13 and Table 1.

Example 1 Example 2 Example 4 Comparative Example 2 Comparative Example 3 Capacitance
(F / g) Energy density
(Wh / kg) Capacitance
(F / g) Energy Density (Wh / kg) Capacitance
(F / g) Energy Density (Wh / kg) Capacitance
(F / g) Energy Density (Wh / kg) Capacitance
(F / g) Energy Density (Wh / kg) 1 ^st 450.01 53.49 541.09 62.73 287.15 31.00 81.00 3.30 81.00 3.30 2 ^nd 405.08 49.18 488.08 57.40 283.71 30.19 81.87 3.53 81.87 3.53 3 ^rd - - - - 273.16 28.58 77.85 3.42 77.85 3.42 4 ^th - - - - 265.25 27.35 74.62 3.31 74.62 3.31 5 ^th 330.65 39.92 405.08 48.14 257.27 26.50 64.06 3.17 64.06 3.17

"-" In Table 1 means not measured.

As a result of the measurement, the negative electrode materials of Examples 1, 2, and 4 showed higher energy density with higher capacitance than Comparative Examples 2 and 3. Among them, Examples 1 and 2 including CNT as a conductive inorganic material showed a high energy density of 50 Wh / kg or higher with a high capacitance of 450 F / g or higher due to the high electrical conductivity of CNT, and 300 F even after 5 cycles. a capacitance of at least / g and an energy density of at least 30 Wh / kg. Such excellent capacitance and energy density characteristics are due to the large increase in specific surface area as the negative electrode materials of Examples 1 and 2 have a layered structure. On the other hand, in the case of Example 4 including graphene instead of CNT, due to the difference in the low charge transfer capacity and the conductive path (conducting path) compared to Examples 1 and 2, it showed a relatively low capacitance and energy density .

In addition, in Comparative Example 2, which does not contain a conductive inorganic material such as CNT, the absence of a conductive bridge to be present between the particles, the charge capacity is significantly reduced compared to the embodiment as the charge transfer capacity is reduced And energy density, and after 5 cycles, the difference in capacitance and energy density became larger.

In addition, Comparative Example 3, which includes only a composite of a metal oxide and a conductive inorganic material without a doping element, showed a significantly reduced capacitance and energy density due to a decrease in charge mobility compared to an example including a doping element.

Experimental Example 3

In the same manner as in Experimental Example 2, to prepare an electrode using the negative electrode material of Examples 1 to 3, and Comparative Example 1, impregnated and stabilized 1M Li ₂ SO ₄ electrolyte to each electrode prepared Using the platinum counter electrode and the SCE reference electrode, the output characteristics were evaluated in the voltage range of -1.2 to -0.2V, under the conditions of 1 to 20 kW / kg and 1 to 30 A / g. The results are shown in FIG.

Experimental results show that the negative electrode materials of Examples 1 to 3, which contain a composite of vanadium oxide-carbon case material doped with Cu, Al, or Mn, have better output characteristics than the negative electrode material of Comparative Example 1, which is undoped. Indicated. From these results, it can be seen that the output characteristics of the electrode material can be further improved by doping the vanadium oxide-carbon-based composite material.

Experimental Example 4

Each electrode comprising the negative electrode materials of Examples 1 to 3 and Comparative Example 1 prepared above was vacuum-impregnated and stabilized with Li ₂ SO ₄ electrolyte, and then circulated scanning using a platinum counter electrode and an SCE reference electrode. Dislocation experiments were performed. In the voltage range of -1.2--0.2V, it measured with the potential scan speed of 10 mA / s. The results are shown in Table 2 below.

Doping element Capacitance (F / g @ 1.33 A / g) Example 1 Al 363 Example 2 Mn 442 Example 3 Cu 321 Comparative Example 1 - 318

As a result, Examples 1 to 3 showed improved capacitance compared to Comparative Example 1, in particular, Examples 1 and 2 doped with Al or Mn showed a greatly increased capacitance of 350 F / g or more. On the other hand, in the case of Example 3 doped with Cu, the capacitance was reduced compared to Examples 1 and 2 due to the relatively low charge mobility despite the metal doping.

Claims (20)

A complex of a metal oxide-conductive inorganic material including a metal oxide and a conductive inorganic material combined with the metal oxide,
The metal oxide has a plate-like structure,
The composite has a plate-like laminated structure in which a conductive inorganic material is interposed between a plurality of the metal oxides of the plate-like structure, and is doped with at least one doping element selected from the group consisting of transition metals and amphoteric metal elements. Cathode material.
delete The negative electrode material of claim 1, wherein the composite is doped with one or more doping elements selected from the group consisting of Mn, Cr, Cu, Mo, Ni, Ti, Al, Zn, Sn, and Bi.
The negative electrode material of claim 1, wherein the doping element is included in an amount of 0.1 to 30 atomic% with respect to the total content of the elements constituting the composite.
The negative electrode material of claim 1, wherein the metal oxide is an oxide including at least one metal selected from the group consisting of V, Sn, Ru, Ir, Ta, Mn, Mo, and Ti.
The negative electrode material of claim 1, wherein the conductive inorganic material includes at least one selected from the group consisting of a carbonaceous material and maxine.
The method of claim 1,
The conductive inorganic material includes any one or two or more carbon-based material selected from the group consisting of carbon nanotubes, carbon nanofibers, carbon nanorods, steam grown carbon fibers, graphene, and activated carbon, negative electrode material for water capacitors .
The negative electrode material of claim 1, wherein the metal oxide is included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the conductive inorganic material.
The negative electrode material of claim 1, wherein the metal oxide includes vanadium oxide, the conductive inorganic material includes carbon nanotubes, and the composite material is doped with at least one of Al and Mn. .
Mixing a metal oxide, a conductive inorganic material and a raw material of a doping element, and then reacting by adding a carboxylic acid complexing agent; And
Heat-treating the resulting reactants,
The metal oxide has a plate-like structure, the method of producing a negative electrode material for water capacitors of claim 1.
The negative electrode material of claim 10, wherein the raw material of the doping element comprises one or a mixture of two or more selected from the group consisting of sulfate, nitrate, chloride, acetate and carbonate containing a doping element. Manufacturing method.
The method of manufacturing a negative electrode material for a water capacitor according to claim 10, wherein the raw material of the doping element is a sulfate including at least one of Mn and Al.
The method of claim 10, wherein the carboxylic acid-based complexing agent is selected from the group consisting of monocarboxylic acid, dicarboxylic acid, trifunctional or higher polyhydric carboxylic acid, and amino acid.
The method of claim 10, wherein the carboxylic acid-based complexing agent is selected from the group consisting of L-aspartic acid, acetic acid, citric acid, and mixtures thereof.
The method of claim 10, wherein after the mixing of the metal oxide, the conductive inorganic material and the raw material of the doping element, an alcohol compound is further added before the carboxylic acid complexing agent is added.
The method of claim 10, wherein the carboxylic acid-based complexing agent is introduced into a solution dissolved in a mixture of water and an acid.
The method of claim 10, further comprising lyophilizing the resulting reactant before the heat treatment.
The method of claim 10, wherein the heat treatment is performed at 250 to 350 ° C. 12.
A negative electrode for a water capacitor, comprising the negative electrode material according to any one of claims 1 to 10.
A water capacitor comprising the negative electrode material according to claim 1.

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